This invention relates to a method for automatically determining color control conditions such as a highlight point, a shadow point, gradation control, color correction, and so forth, for color separation films or plates of primary colors for use in a picture reproducing machine.
Generally, when an original picture is color-separated by a picture reproducing machine such as a color scanner and a color facsimile device to obtain color separation films or plates, since the density range of the original color picture is generally different from the reproducible density range of the picture reproducing machine, proper highlight and shadow points in the original picture are selectively determined, and thereafter their densities are adjusted to the picture reproducing machine, thereby adjusting the density range of the original picture to the reproducible density range of the picture reproducing machine. Then, when the color separation films are made by the picture reproducing machine, in order to reproduce a better reproduction picture, the gradation control, the color correction, and so forth, are also performed.
Even by a skilled operator it is not easy to set up such basic color control conditions such as the highlight point, the shadow point, the gradation control, the color correction, and so forth, of the picture reproducing machine such as a color scanner.
When the highlight point and the shadow point on the original picture, in particular, a 35 mm film which is often used nowadays, are selected, it is difficult to distinguish the highlight and the shadow points from others having similar intermediate densities, and to distinguish a highlight point from a catchlight point. Further, there are some points very similar in appearance, in the same original picture, and thus it requires great skill to determine the highlight and the shadow points. The operator is likely to make a mistake.
As regards the gradation control, no standard method has heretofore been realized, and now, in practice, the operator judges and determines the tone of the original picture by himself, and accordingly he is likely to make a mistake.
In addition, concerning the color correction, when the color of the certain area of the original picture is changed, or a delicate color correction is required, in practice, it is done by the operator while he observes a monitor or the output values of the picture reproducing machine, or by a skilled operator according to his knowledge and experience. Hence, he is also apt to make a mistake.